Yes Microsoft Flight Simulator 2020 does support HDR if you see my video on YouTube
https://www.youtube.com/watch?v=ck6KJGchhjo&t=8s this is a straight recording (that work) from Microsoft Simulator 2020 in 4k HDR straight form action!4 no Rendering was done and form YouTube id does show in 4k HDR ( cuz now YouTube does support HDR video) so no rendering was done and this exemple did work but for 1 good recording from Action!4 i got 5 bad ones that like i was saying did Studer , mosaic , slow downs pixilated and HDR randomly not showing , and like i was saying i will post an exemple of what i am experiencing with Microsoft Flight Simulator 2020